The first thing to remember with this and hundreds (thousands) of similar books of this era is that they are not primary source records. They are assemblages of information from an era when this type of research was a far different thing than it would be today (that is not in any way meant to demean the research that went into it).
After scanning the early parts of the book, this one is not making any of the often seen fantastical ancestral claims somewhat common for the era. The early discussion is underpinned by documents. When you get to the second generation, you are given quite a lot of information but are not being given the underlying sources for the information. So, I would take this information and see what of it you can now support by primary source documentation found elsewhere. I would use it as a roadmap. Much of it may be accurate, some of it may not be. If you start finding information that cannot be supported by primary sources but is also not refuted by primary sources, come back to G2G and pose questions about that where any number of people can assist you.